Microsieves are known in the art. In this description the term “microsieve” is used as a general name for products having apertures with dimensions in the micron or submicron range, irrespective of the use of the product. Such sieve materials are often made of plastic or of ceramic material, for example by means of lithographic techniques. See, for example, WO 02/43937 A2 and NL-1006118 C. In the case of these known flat sieve materials with two main surfaces which are substantially parallel the sieve apertures are through apertures extending in a straight line from the one main surface to the other main surface of the sieve material. In other words, such a sieve aperture has an inlet on one of the two main surfaces and extends linearly through the thickness of the sieve material to the other main surface, where the aperture opens into an outlet.
In the art there is also a need for microsieves made of metal. Conventional electroforming techniques for producing sieves for use in screen printing technology are not adequate for the production of such metal microsieves because the required accuracy of sieve apertures with small cross-sectional dimensions cannot be achieved with those techniques, since the photoresist distribution which largely determines the sieve aperture characteristics is too great or, if use is made of the overgrowth principle (in which metal grows partially over insulating areas on a die), the distribution in the deposited metal thickness is too great to achieve apertures in the micron or submicron range.
The object of the present invention is to provide such sieve material of metal, and also a method for its production.